Rotary machines typically utilize vane motors that are pneumatically powered to cause rotation of the output shaft. As is well known these machines comprise a cylinder, sometimes referred to as a casing and an eccentrically mounted spindle relative to the bore of the cylinder, sometimes referred to as a rotor. The cylinder is stationary and through apertures in the cylinder lead pressurized air to impinge on the working face of the reciprocating vanes mounted in slots formed in the spindle to cause the spindle to rotate and then exhaust the spent air through additional holes formed in the cylinder. The outer edge of the vanes is in contact with or in close proximity to the inner surface of the cylinder and the spindle during the power stroke of the vane motor transitions from close to the inner surface of the cylinder bore toward the furthest distance there from and during the exhaust portion of the stroke the spindle transitions from the furthest point away the inner surface of the cylinder toward the closest point thereto. Heretofore, the cylinder had apertures formed therein that were configured in the shape of slots. The pressurized air that is admitted to the spindle impinge on the working face of the vanes to cause them to rotate the spindle.
I have found that the vane motor can be enhanced by substituting cylindrical holes for the slots, providing a series of axially spaced holes defining the inlet to the vane motor, providing a pressurized air axial passageway in the cylinder to feed pressurized air to these inlet holes, by-passing the upstream portion of the inlet holes and providing circumferential slots in the cylinder that feed a portion of the pressurized air to the inlet holes, discharging that portion of the pressurized air to circulate over the bearings supporting the spindle and providing another axial passageway for returning the remaining pressurized air to the inlet holes and providing a plurality of judiciously located discharge cylindrical holes to discharge the spent air after performing work on the vanes. The routing of the pressurized air and spent air flowing into and out of the cylinder is done in such a way as to reduce both heat and noise that would otherwise be generated by the vane motor. Suffice it to say that this invention affords the following features that serve to enhance the vane motor and in certain medical instruments, such as a surgical drill, this invention reduces heat, vibration, noise and allows for a smaller envelope size that goes to the comfort and feel in the hands of a surgeon.                1. Smaller motor spherical ball bearing located at the fore end of the power cylinder provides a cavity within the housing to re-circulate the power cylinder's working compressed air which contributes to lowering the temperature of the bearing and affording improvements to the vibrations and heat characteristics.        2. Cylinder input holes are oriented relative to the spindle vanes so as to increase input airflow acting on the vane's working surface.        3. Slots in the cylinder formed adjacent to the inlet holes cool the cylinder before entering the vane motor.        4. A portion of the inlet air to the motor is diverted to flow to the front bearing and toward the aft end so as to air cool the front bearing housing and air cool the cylinder.        5. Additional increased power is obtained by the orientation of the exhaust holes in the vane motor relative to the inlet holes.        6. Minimizing vane wear by the uniform distribution of the vane's contact area with the cylinder.        